Flanker Sean O'Brien knows Ireland cannot afford "to go on a manhunt" for England fly-half Owen Farrell.
The Irish can't afford to give away penalties like they did against Wales. Mistakes cost points when Farrell is around.
"Our discipline is going to have to be spot-on. I don't think we can go on a manhunt for him. If we start going after him, holes will open up beside him or around him. He'll know that," said O'Brien.
There is something truly agricultural about the way Sean O'Brien mows down defenders and cuts down carriers. It comes so naturally to him.
The Carlow farmer is more likely to spend his time pulling calves from cows than examining the merits of his performance or those of his next direct opponent, England captain Chris Robshaw, until he sits down to review and preview.
The statistics were there to support his all-embracing performance for Ireland against Wales last Saturday – 23 tackles, the most, and 12 carries, the most.
"It wasn't one individual running around making all the tackles. Our system was good and we trusted each other. That is why we held them out," said O'Brien. "It has a lot to do with the team playing well. In the first half, we were going forward. We got momentum. In the second half, we were defending well together."
The workload is not likely to diminish against England unless Ireland can hold onto the ball when they have it.
It doesn't seem to bother O'Brien whether he has to hit or be hit.
"It is the same process you go through every week, you know. You make five or six more tackles than you would on a normal day. That's all it really is," he said.
"You body is not overly different than it is any other week, although the stats might show that. If you make 10 hard tackles, 20 is not going to kill you."
Certainly, the wall of noise will hit O'Brien straight between the ears tomorrow afternoon as two countries bent on domination engage in a war of territory and points.
The Irish flanker was not going to bite down on the temptation to build up old hostilities. The English are just another band of brothers standing in his way.
"I don't think it is the most special (match for Irish players). I certainly think it is probably more special off the field for the people, the fans, for the rivalry there," he said.
"To us, it is another international game.
"It is another chance to express ourselves and look for that consistency that we've been looking for.
"We don't go into the 'them and us' thing anymore. It is about looking after ourselves first and foremost. If we do that, the result should come our way."
O'Brien comprehensively outplayed one British & Irish Lions captaincy candidate in Sam Warburton last week. He will confront another in Robshaw.
"He's a very good player. He's a leader. He has been there with Harlequins for a long time as well. He's a threat. Any international back rower you come up against is a good player and he's no different."